A passive optical network (PON) is a point-to-multipoint network topology structure, and usually includes an optical line terminal (OLT) in a central office, a plurality of optical network units (ONU) at a user end, and an optical distribution network (ODN) located the OLT and the ONU.
In a PON system, a newly added ONU needs to complete registration and activation at an OLT before sending an upstream service data to the OLT over an upstream channel. In an Ethernet passive optical network (EPON) system, an OLT receives, by creating a quiet zone, a registration response packet sent by a newly added ONU over an upstream channel, allocates a logical link identifier (LLID) to the newly added ONU based on a Media Access Control (MAC) address carried in the registration response packet, and completes ranging of the newly added ONU. In a gigabit-capable passive optical network (GPON) system, an OLT receives, by creating a quiet zone, a registration response packet sent by a newly added ONU, allocates an ONU ID based on a serial number (SN) carried in the registration response packet, and further completes ranging of the newly added ONU.
After being registered, a registered ONU sends upstream service data to an OLT over an upstream channel in a Time Division Multiple Access manner (TDMA) and based on an upstream sending timeslot allocated by the OLT, to prevent upstream service data sent by different ONUs from conflicting with each other on the upstream channel. In addition, to avoid a conflict between a registration response packet and the upstream service data on the upstream channel, during registration of a newly added ONU, the OLT stops providing a bandwidth grant for a registered ONU, that is, the registered ONU stops sending upstream service data.
In the PON system, the registered ONU needs to send the upstream service data only after the quiet zones ends. As a result, the upstream service data is sent with a relatively large delay, and a system delay requirement of a low-delay service cannot be satisfied.